Shoaib Ahmed / Mbed 2 deprecated uzairkhan

Final 350 project

Dependencies:   uzair Camera_LS_Y201 F7_Ethernet LCD_DISCO_F746NG NetworkAPI SDFileSystem mbed

includes/jidctfst.c@0:791a779d6220, 2017-07-31 (annotated)

Committer:
shoaib_ahmed
Date:
Mon Jul 31 09:16:35 2017 +0000
Revision:
0:791a779d6220
final project;

Who changed what in which revision?

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shoaib_ahmed 0:791a779d6220 1 /*
shoaib_ahmed 0:791a779d6220 2 * jidctfst.c
shoaib_ahmed 0:791a779d6220 3 *
shoaib_ahmed 0:791a779d6220 4 * Copyright (C) 1994-1998, Thomas G. Lane.
shoaib_ahmed 0:791a779d6220 5 * Modified 2015 by Guido Vollbeding.
shoaib_ahmed 0:791a779d6220 6 * This file is part of the Independent JPEG Group's software.
shoaib_ahmed 0:791a779d6220 7 * For conditions of distribution and use, see the accompanying README file.
shoaib_ahmed 0:791a779d6220 8 *
shoaib_ahmed 0:791a779d6220 9 * This file contains a fast, not so accurate integer implementation of the
shoaib_ahmed 0:791a779d6220 10 * inverse DCT (Discrete Cosine Transform). In the IJG code, this routine
shoaib_ahmed 0:791a779d6220 11 * must also perform dequantization of the input coefficients.
shoaib_ahmed 0:791a779d6220 12 *
shoaib_ahmed 0:791a779d6220 13 * A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT
shoaib_ahmed 0:791a779d6220 14 * on each row (or vice versa, but it's more convenient to emit a row at
shoaib_ahmed 0:791a779d6220 15 * a time). Direct algorithms are also available, but they are much more
shoaib_ahmed 0:791a779d6220 16 * complex and seem not to be any faster when reduced to code.
shoaib_ahmed 0:791a779d6220 17 *
shoaib_ahmed 0:791a779d6220 18 * This implementation is based on Arai, Agui, and Nakajima's algorithm for
shoaib_ahmed 0:791a779d6220 19 * scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in
shoaib_ahmed 0:791a779d6220 20 * Japanese, but the algorithm is described in the Pennebaker & Mitchell
shoaib_ahmed 0:791a779d6220 21 * JPEG textbook (see REFERENCES section in file README). The following code
shoaib_ahmed 0:791a779d6220 22 * is based directly on figure 4-8 in P&M.
shoaib_ahmed 0:791a779d6220 23 * While an 8-point DCT cannot be done in less than 11 multiplies, it is
shoaib_ahmed 0:791a779d6220 24 * possible to arrange the computation so that many of the multiplies are
shoaib_ahmed 0:791a779d6220 25 * simple scalings of the final outputs. These multiplies can then be
shoaib_ahmed 0:791a779d6220 26 * folded into the multiplications or divisions by the JPEG quantization
shoaib_ahmed 0:791a779d6220 27 * table entries. The AA&N method leaves only 5 multiplies and 29 adds
shoaib_ahmed 0:791a779d6220 28 * to be done in the DCT itself.
shoaib_ahmed 0:791a779d6220 29 * The primary disadvantage of this method is that with fixed-point math,
shoaib_ahmed 0:791a779d6220 30 * accuracy is lost due to imprecise representation of the scaled
shoaib_ahmed 0:791a779d6220 31 * quantization values. The smaller the quantization table entry, the less
shoaib_ahmed 0:791a779d6220 32 * precise the scaled value, so this implementation does worse with high-
shoaib_ahmed 0:791a779d6220 33 * quality-setting files than with low-quality ones.
shoaib_ahmed 0:791a779d6220 34 */
shoaib_ahmed 0:791a779d6220 35
shoaib_ahmed 0:791a779d6220 36 #define JPEG_INTERNALS
shoaib_ahmed 0:791a779d6220 37 #include "jinclude.h"
shoaib_ahmed 0:791a779d6220 38 #include "jpeglib.h"
shoaib_ahmed 0:791a779d6220 39 #include "jdct.h" /* Private declarations for DCT subsystem */
shoaib_ahmed 0:791a779d6220 40
shoaib_ahmed 0:791a779d6220 41 #ifdef DCT_IFAST_SUPPORTED
shoaib_ahmed 0:791a779d6220 42
shoaib_ahmed 0:791a779d6220 43
shoaib_ahmed 0:791a779d6220 44 /*
shoaib_ahmed 0:791a779d6220 45 * This module is specialized to the case DCTSIZE = 8.
shoaib_ahmed 0:791a779d6220 46 */
shoaib_ahmed 0:791a779d6220 47
shoaib_ahmed 0:791a779d6220 48 #if DCTSIZE != 8
shoaib_ahmed 0:791a779d6220 49 Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
shoaib_ahmed 0:791a779d6220 50 #endif
shoaib_ahmed 0:791a779d6220 51
shoaib_ahmed 0:791a779d6220 52
shoaib_ahmed 0:791a779d6220 53 /* Scaling decisions are generally the same as in the LL&M algorithm;
shoaib_ahmed 0:791a779d6220 54 * see jidctint.c for more details. However, we choose to descale
shoaib_ahmed 0:791a779d6220 55 * (right shift) multiplication products as soon as they are formed,
shoaib_ahmed 0:791a779d6220 56 * rather than carrying additional fractional bits into subsequent additions.
shoaib_ahmed 0:791a779d6220 57 * This compromises accuracy slightly, but it lets us save a few shifts.
shoaib_ahmed 0:791a779d6220 58 * More importantly, 16-bit arithmetic is then adequate (for 8-bit samples)
shoaib_ahmed 0:791a779d6220 59 * everywhere except in the multiplications proper; this saves a good deal
shoaib_ahmed 0:791a779d6220 60 * of work on 16-bit-int machines.
shoaib_ahmed 0:791a779d6220 61 *
shoaib_ahmed 0:791a779d6220 62 * The dequantized coefficients are not integers because the AA&N scaling
shoaib_ahmed 0:791a779d6220 63 * factors have been incorporated. We represent them scaled up by PASS1_BITS,
shoaib_ahmed 0:791a779d6220 64 * so that the first and second IDCT rounds have the same input scaling.
shoaib_ahmed 0:791a779d6220 65 * For 8-bit JSAMPLEs, we choose IFAST_SCALE_BITS = PASS1_BITS so as to
shoaib_ahmed 0:791a779d6220 66 * avoid a descaling shift; this compromises accuracy rather drastically
shoaib_ahmed 0:791a779d6220 67 * for small quantization table entries, but it saves a lot of shifts.
shoaib_ahmed 0:791a779d6220 68 * For 12-bit JSAMPLEs, there's no hope of using 16x16 multiplies anyway,
shoaib_ahmed 0:791a779d6220 69 * so we use a much larger scaling factor to preserve accuracy.
shoaib_ahmed 0:791a779d6220 70 *
shoaib_ahmed 0:791a779d6220 71 * A final compromise is to represent the multiplicative constants to only
shoaib_ahmed 0:791a779d6220 72 * 8 fractional bits, rather than 13. This saves some shifting work on some
shoaib_ahmed 0:791a779d6220 73 * machines, and may also reduce the cost of multiplication (since there
shoaib_ahmed 0:791a779d6220 74 * are fewer one-bits in the constants).
shoaib_ahmed 0:791a779d6220 75 */
shoaib_ahmed 0:791a779d6220 76
shoaib_ahmed 0:791a779d6220 77 #if BITS_IN_JSAMPLE == 8
shoaib_ahmed 0:791a779d6220 78 #define CONST_BITS 8
shoaib_ahmed 0:791a779d6220 79 #define PASS1_BITS 2
shoaib_ahmed 0:791a779d6220 80 #else
shoaib_ahmed 0:791a779d6220 81 #define CONST_BITS 8
shoaib_ahmed 0:791a779d6220 82 #define PASS1_BITS 1 /* lose a little precision to avoid overflow */
shoaib_ahmed 0:791a779d6220 83 #endif
shoaib_ahmed 0:791a779d6220 84
shoaib_ahmed 0:791a779d6220 85 /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
shoaib_ahmed 0:791a779d6220 86 * causing a lot of useless floating-point operations at run time.
shoaib_ahmed 0:791a779d6220 87 * To get around this we use the following pre-calculated constants.
shoaib_ahmed 0:791a779d6220 88 * If you change CONST_BITS you may want to add appropriate values.
shoaib_ahmed 0:791a779d6220 89 * (With a reasonable C compiler, you can just rely on the FIX() macro...)
shoaib_ahmed 0:791a779d6220 90 */
shoaib_ahmed 0:791a779d6220 91
shoaib_ahmed 0:791a779d6220 92 #if CONST_BITS == 8
shoaib_ahmed 0:791a779d6220 93 #define FIX_1_082392200 ((INT32) 277) /* FIX(1.082392200) */
shoaib_ahmed 0:791a779d6220 94 #define FIX_1_414213562 ((INT32) 362) /* FIX(1.414213562) */
shoaib_ahmed 0:791a779d6220 95 #define FIX_1_847759065 ((INT32) 473) /* FIX(1.847759065) */
shoaib_ahmed 0:791a779d6220 96 #define FIX_2_613125930 ((INT32) 669) /* FIX(2.613125930) */
shoaib_ahmed 0:791a779d6220 97 #else
shoaib_ahmed 0:791a779d6220 98 #define FIX_1_082392200 FIX(1.082392200)
shoaib_ahmed 0:791a779d6220 99 #define FIX_1_414213562 FIX(1.414213562)
shoaib_ahmed 0:791a779d6220 100 #define FIX_1_847759065 FIX(1.847759065)
shoaib_ahmed 0:791a779d6220 101 #define FIX_2_613125930 FIX(2.613125930)
shoaib_ahmed 0:791a779d6220 102 #endif
shoaib_ahmed 0:791a779d6220 103
shoaib_ahmed 0:791a779d6220 104
shoaib_ahmed 0:791a779d6220 105 /* We can gain a little more speed, with a further compromise in accuracy,
shoaib_ahmed 0:791a779d6220 106 * by omitting the addition in a descaling shift. This yields an incorrectly
shoaib_ahmed 0:791a779d6220 107 * rounded result half the time...
shoaib_ahmed 0:791a779d6220 108 */
shoaib_ahmed 0:791a779d6220 109
shoaib_ahmed 0:791a779d6220 110 #ifndef USE_ACCURATE_ROUNDING
shoaib_ahmed 0:791a779d6220 111 #undef DESCALE
shoaib_ahmed 0:791a779d6220 112 #define DESCALE(x,n) RIGHT_SHIFT(x, n)
shoaib_ahmed 0:791a779d6220 113 #endif
shoaib_ahmed 0:791a779d6220 114
shoaib_ahmed 0:791a779d6220 115
shoaib_ahmed 0:791a779d6220 116 /* Multiply a DCTELEM variable by an INT32 constant, and immediately
shoaib_ahmed 0:791a779d6220 117 * descale to yield a DCTELEM result.
shoaib_ahmed 0:791a779d6220 118 */
shoaib_ahmed 0:791a779d6220 119
shoaib_ahmed 0:791a779d6220 120 #define MULTIPLY(var,const) ((DCTELEM) DESCALE((var) * (const), CONST_BITS))
shoaib_ahmed 0:791a779d6220 121
shoaib_ahmed 0:791a779d6220 122
shoaib_ahmed 0:791a779d6220 123 /* Dequantize a coefficient by multiplying it by the multiplier-table
shoaib_ahmed 0:791a779d6220 124 * entry; produce a DCTELEM result. For 8-bit data a 16x16->16
shoaib_ahmed 0:791a779d6220 125 * multiplication will do. For 12-bit data, the multiplier table is
shoaib_ahmed 0:791a779d6220 126 * declared INT32, so a 32-bit multiply will be used.
shoaib_ahmed 0:791a779d6220 127 */
shoaib_ahmed 0:791a779d6220 128
shoaib_ahmed 0:791a779d6220 129 #if BITS_IN_JSAMPLE == 8
shoaib_ahmed 0:791a779d6220 130 #define DEQUANTIZE(coef,quantval) (((IFAST_MULT_TYPE) (coef)) * (quantval))
shoaib_ahmed 0:791a779d6220 131 #else
shoaib_ahmed 0:791a779d6220 132 #define DEQUANTIZE(coef,quantval) \
shoaib_ahmed 0:791a779d6220 133 DESCALE((coef)*(quantval), IFAST_SCALE_BITS-PASS1_BITS)
shoaib_ahmed 0:791a779d6220 134 #endif
shoaib_ahmed 0:791a779d6220 135
shoaib_ahmed 0:791a779d6220 136
shoaib_ahmed 0:791a779d6220 137 /*
shoaib_ahmed 0:791a779d6220 138 * Perform dequantization and inverse DCT on one block of coefficients.
shoaib_ahmed 0:791a779d6220 139 *
shoaib_ahmed 0:791a779d6220 140 * cK represents cos(K*pi/16).
shoaib_ahmed 0:791a779d6220 141 */
shoaib_ahmed 0:791a779d6220 142
shoaib_ahmed 0:791a779d6220 143 GLOBAL(void)
shoaib_ahmed 0:791a779d6220 144 jpeg_idct_ifast (j_decompress_ptr cinfo, jpeg_component_info * compptr,
shoaib_ahmed 0:791a779d6220 145 JCOEFPTR coef_block,
shoaib_ahmed 0:791a779d6220 146 JSAMPARRAY output_buf, JDIMENSION output_col)
shoaib_ahmed 0:791a779d6220 147 {
shoaib_ahmed 0:791a779d6220 148 DCTELEM tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
shoaib_ahmed 0:791a779d6220 149 DCTELEM tmp10, tmp11, tmp12, tmp13;
shoaib_ahmed 0:791a779d6220 150 DCTELEM z5, z10, z11, z12, z13;
shoaib_ahmed 0:791a779d6220 151 JCOEFPTR inptr;
shoaib_ahmed 0:791a779d6220 152 IFAST_MULT_TYPE * quantptr;
shoaib_ahmed 0:791a779d6220 153 int * wsptr;
shoaib_ahmed 0:791a779d6220 154 JSAMPROW outptr;
shoaib_ahmed 0:791a779d6220 155 JSAMPLE *range_limit = IDCT_range_limit(cinfo);
shoaib_ahmed 0:791a779d6220 156 int ctr;
shoaib_ahmed 0:791a779d6220 157 int workspace[DCTSIZE2]; /* buffers data between passes */
shoaib_ahmed 0:791a779d6220 158 SHIFT_TEMPS /* for DESCALE */
shoaib_ahmed 0:791a779d6220 159 ISHIFT_TEMPS /* for IRIGHT_SHIFT */
shoaib_ahmed 0:791a779d6220 160
shoaib_ahmed 0:791a779d6220 161 /* Pass 1: process columns from input, store into work array. */
shoaib_ahmed 0:791a779d6220 162
shoaib_ahmed 0:791a779d6220 163 inptr = coef_block;
shoaib_ahmed 0:791a779d6220 164 quantptr = (IFAST_MULT_TYPE *) compptr->dct_table;
shoaib_ahmed 0:791a779d6220 165 wsptr = workspace;
shoaib_ahmed 0:791a779d6220 166 for (ctr = DCTSIZE; ctr > 0; ctr--) {
shoaib_ahmed 0:791a779d6220 167 /* Due to quantization, we will usually find that many of the input
shoaib_ahmed 0:791a779d6220 168 * coefficients are zero, especially the AC terms. We can exploit this
shoaib_ahmed 0:791a779d6220 169 * by short-circuiting the IDCT calculation for any column in which all
shoaib_ahmed 0:791a779d6220 170 * the AC terms are zero. In that case each output is equal to the
shoaib_ahmed 0:791a779d6220 171 * DC coefficient (with scale factor as needed).
shoaib_ahmed 0:791a779d6220 172 * With typical images and quantization tables, half or more of the
shoaib_ahmed 0:791a779d6220 173 * column DCT calculations can be simplified this way.
shoaib_ahmed 0:791a779d6220 174 */
shoaib_ahmed 0:791a779d6220 175
shoaib_ahmed 0:791a779d6220 176 if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
shoaib_ahmed 0:791a779d6220 177 inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*4] == 0 &&
shoaib_ahmed 0:791a779d6220 178 inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 &&
shoaib_ahmed 0:791a779d6220 179 inptr[DCTSIZE*7] == 0) {
shoaib_ahmed 0:791a779d6220 180 /* AC terms all zero */
shoaib_ahmed 0:791a779d6220 181 int dcval = (int) DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
shoaib_ahmed 0:791a779d6220 182
shoaib_ahmed 0:791a779d6220 183 wsptr[DCTSIZE*0] = dcval;
shoaib_ahmed 0:791a779d6220 184 wsptr[DCTSIZE*1] = dcval;
shoaib_ahmed 0:791a779d6220 185 wsptr[DCTSIZE*2] = dcval;
shoaib_ahmed 0:791a779d6220 186 wsptr[DCTSIZE*3] = dcval;
shoaib_ahmed 0:791a779d6220 187 wsptr[DCTSIZE*4] = dcval;
shoaib_ahmed 0:791a779d6220 188 wsptr[DCTSIZE*5] = dcval;
shoaib_ahmed 0:791a779d6220 189 wsptr[DCTSIZE*6] = dcval;
shoaib_ahmed 0:791a779d6220 190 wsptr[DCTSIZE*7] = dcval;
shoaib_ahmed 0:791a779d6220 191
shoaib_ahmed 0:791a779d6220 192 inptr++; /* advance pointers to next column */
shoaib_ahmed 0:791a779d6220 193 quantptr++;
shoaib_ahmed 0:791a779d6220 194 wsptr++;
shoaib_ahmed 0:791a779d6220 195 continue;
shoaib_ahmed 0:791a779d6220 196 }
shoaib_ahmed 0:791a779d6220 197
shoaib_ahmed 0:791a779d6220 198 /* Even part */
shoaib_ahmed 0:791a779d6220 199
shoaib_ahmed 0:791a779d6220 200 tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
shoaib_ahmed 0:791a779d6220 201 tmp1 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
shoaib_ahmed 0:791a779d6220 202 tmp2 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]);
shoaib_ahmed 0:791a779d6220 203 tmp3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);
shoaib_ahmed 0:791a779d6220 204
shoaib_ahmed 0:791a779d6220 205 tmp10 = tmp0 + tmp2; /* phase 3 */
shoaib_ahmed 0:791a779d6220 206 tmp11 = tmp0 - tmp2;
shoaib_ahmed 0:791a779d6220 207
shoaib_ahmed 0:791a779d6220 208 tmp13 = tmp1 + tmp3; /* phases 5-3 */
shoaib_ahmed 0:791a779d6220 209 tmp12 = MULTIPLY(tmp1 - tmp3, FIX_1_414213562) - tmp13; /* 2*c4 */
shoaib_ahmed 0:791a779d6220 210
shoaib_ahmed 0:791a779d6220 211 tmp0 = tmp10 + tmp13; /* phase 2 */
shoaib_ahmed 0:791a779d6220 212 tmp3 = tmp10 - tmp13;
shoaib_ahmed 0:791a779d6220 213 tmp1 = tmp11 + tmp12;
shoaib_ahmed 0:791a779d6220 214 tmp2 = tmp11 - tmp12;
shoaib_ahmed 0:791a779d6220 215
shoaib_ahmed 0:791a779d6220 216 /* Odd part */
shoaib_ahmed 0:791a779d6220 217
shoaib_ahmed 0:791a779d6220 218 tmp4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
shoaib_ahmed 0:791a779d6220 219 tmp5 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
shoaib_ahmed 0:791a779d6220 220 tmp6 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
shoaib_ahmed 0:791a779d6220 221 tmp7 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
shoaib_ahmed 0:791a779d6220 222
shoaib_ahmed 0:791a779d6220 223 z13 = tmp6 + tmp5; /* phase 6 */
shoaib_ahmed 0:791a779d6220 224 z10 = tmp6 - tmp5;
shoaib_ahmed 0:791a779d6220 225 z11 = tmp4 + tmp7;
shoaib_ahmed 0:791a779d6220 226 z12 = tmp4 - tmp7;
shoaib_ahmed 0:791a779d6220 227
shoaib_ahmed 0:791a779d6220 228 tmp7 = z11 + z13; /* phase 5 */
shoaib_ahmed 0:791a779d6220 229 tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */
shoaib_ahmed 0:791a779d6220 230
shoaib_ahmed 0:791a779d6220 231 z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */
shoaib_ahmed 0:791a779d6220 232 tmp10 = z5 - MULTIPLY(z12, FIX_1_082392200); /* 2*(c2-c6) */
shoaib_ahmed 0:791a779d6220 233 tmp12 = z5 - MULTIPLY(z10, FIX_2_613125930); /* 2*(c2+c6) */
shoaib_ahmed 0:791a779d6220 234
shoaib_ahmed 0:791a779d6220 235 tmp6 = tmp12 - tmp7; /* phase 2 */
shoaib_ahmed 0:791a779d6220 236 tmp5 = tmp11 - tmp6;
shoaib_ahmed 0:791a779d6220 237 tmp4 = tmp10 - tmp5;
shoaib_ahmed 0:791a779d6220 238
shoaib_ahmed 0:791a779d6220 239 wsptr[DCTSIZE*0] = (int) (tmp0 + tmp7);
shoaib_ahmed 0:791a779d6220 240 wsptr[DCTSIZE*7] = (int) (tmp0 - tmp7);
shoaib_ahmed 0:791a779d6220 241 wsptr[DCTSIZE*1] = (int) (tmp1 + tmp6);
shoaib_ahmed 0:791a779d6220 242 wsptr[DCTSIZE*6] = (int) (tmp1 - tmp6);
shoaib_ahmed 0:791a779d6220 243 wsptr[DCTSIZE*2] = (int) (tmp2 + tmp5);
shoaib_ahmed 0:791a779d6220 244 wsptr[DCTSIZE*5] = (int) (tmp2 - tmp5);
shoaib_ahmed 0:791a779d6220 245 wsptr[DCTSIZE*3] = (int) (tmp3 + tmp4);
shoaib_ahmed 0:791a779d6220 246 wsptr[DCTSIZE*4] = (int) (tmp3 - tmp4);
shoaib_ahmed 0:791a779d6220 247
shoaib_ahmed 0:791a779d6220 248 inptr++; /* advance pointers to next column */
shoaib_ahmed 0:791a779d6220 249 quantptr++;
shoaib_ahmed 0:791a779d6220 250 wsptr++;
shoaib_ahmed 0:791a779d6220 251 }
shoaib_ahmed 0:791a779d6220 252
shoaib_ahmed 0:791a779d6220 253 /* Pass 2: process rows from work array, store into output array.
shoaib_ahmed 0:791a779d6220 254 * Note that we must descale the results by a factor of 8 == 2**3,
shoaib_ahmed 0:791a779d6220 255 * and also undo the PASS1_BITS scaling.
shoaib_ahmed 0:791a779d6220 256 */
shoaib_ahmed 0:791a779d6220 257
shoaib_ahmed 0:791a779d6220 258 wsptr = workspace;
shoaib_ahmed 0:791a779d6220 259 for (ctr = 0; ctr < DCTSIZE; ctr++) {
shoaib_ahmed 0:791a779d6220 260 outptr = output_buf[ctr] + output_col;
shoaib_ahmed 0:791a779d6220 261
shoaib_ahmed 0:791a779d6220 262 /* Add range center and fudge factor for final descale and range-limit. */
shoaib_ahmed 0:791a779d6220 263 z5 = (DCTELEM) wsptr[0] +
shoaib_ahmed 0:791a779d6220 264 ((((DCTELEM) RANGE_CENTER) << (PASS1_BITS+3)) +
shoaib_ahmed 0:791a779d6220 265 (1 << (PASS1_BITS+2)));
shoaib_ahmed 0:791a779d6220 266
shoaib_ahmed 0:791a779d6220 267 /* Rows of zeroes can be exploited in the same way as we did with columns.
shoaib_ahmed 0:791a779d6220 268 * However, the column calculation has created many nonzero AC terms, so
shoaib_ahmed 0:791a779d6220 269 * the simplification applies less often (typically 5% to 10% of the time).
shoaib_ahmed 0:791a779d6220 270 * On machines with very fast multiplication, it's possible that the
shoaib_ahmed 0:791a779d6220 271 * test takes more time than it's worth. In that case this section
shoaib_ahmed 0:791a779d6220 272 * may be commented out.
shoaib_ahmed 0:791a779d6220 273 */
shoaib_ahmed 0:791a779d6220 274
shoaib_ahmed 0:791a779d6220 275 #ifndef NO_ZERO_ROW_TEST
shoaib_ahmed 0:791a779d6220 276 if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && wsptr[4] == 0 &&
shoaib_ahmed 0:791a779d6220 277 wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
shoaib_ahmed 0:791a779d6220 278 /* AC terms all zero */
shoaib_ahmed 0:791a779d6220 279 JSAMPLE dcval = range_limit[(int) IRIGHT_SHIFT(z5, PASS1_BITS+3)
shoaib_ahmed 0:791a779d6220 280 & RANGE_MASK];
shoaib_ahmed 0:791a779d6220 281
shoaib_ahmed 0:791a779d6220 282 outptr[0] = dcval;
shoaib_ahmed 0:791a779d6220 283 outptr[1] = dcval;
shoaib_ahmed 0:791a779d6220 284 outptr[2] = dcval;
shoaib_ahmed 0:791a779d6220 285 outptr[3] = dcval;
shoaib_ahmed 0:791a779d6220 286 outptr[4] = dcval;
shoaib_ahmed 0:791a779d6220 287 outptr[5] = dcval;
shoaib_ahmed 0:791a779d6220 288 outptr[6] = dcval;
shoaib_ahmed 0:791a779d6220 289 outptr[7] = dcval;
shoaib_ahmed 0:791a779d6220 290
shoaib_ahmed 0:791a779d6220 291 wsptr += DCTSIZE; /* advance pointer to next row */
shoaib_ahmed 0:791a779d6220 292 continue;
shoaib_ahmed 0:791a779d6220 293 }
shoaib_ahmed 0:791a779d6220 294 #endif
shoaib_ahmed 0:791a779d6220 295
shoaib_ahmed 0:791a779d6220 296 /* Even part */
shoaib_ahmed 0:791a779d6220 297
shoaib_ahmed 0:791a779d6220 298 tmp10 = z5 + (DCTELEM) wsptr[4];
shoaib_ahmed 0:791a779d6220 299 tmp11 = z5 - (DCTELEM) wsptr[4];
shoaib_ahmed 0:791a779d6220 300
shoaib_ahmed 0:791a779d6220 301 tmp13 = (DCTELEM) wsptr[2] + (DCTELEM) wsptr[6];
shoaib_ahmed 0:791a779d6220 302 tmp12 = MULTIPLY((DCTELEM) wsptr[2] - (DCTELEM) wsptr[6],
shoaib_ahmed 0:791a779d6220 303 FIX_1_414213562) - tmp13; /* 2*c4 */
shoaib_ahmed 0:791a779d6220 304
shoaib_ahmed 0:791a779d6220 305 tmp0 = tmp10 + tmp13;
shoaib_ahmed 0:791a779d6220 306 tmp3 = tmp10 - tmp13;
shoaib_ahmed 0:791a779d6220 307 tmp1 = tmp11 + tmp12;
shoaib_ahmed 0:791a779d6220 308 tmp2 = tmp11 - tmp12;
shoaib_ahmed 0:791a779d6220 309
shoaib_ahmed 0:791a779d6220 310 /* Odd part */
shoaib_ahmed 0:791a779d6220 311
shoaib_ahmed 0:791a779d6220 312 z13 = (DCTELEM) wsptr[5] + (DCTELEM) wsptr[3];
shoaib_ahmed 0:791a779d6220 313 z10 = (DCTELEM) wsptr[5] - (DCTELEM) wsptr[3];
shoaib_ahmed 0:791a779d6220 314 z11 = (DCTELEM) wsptr[1] + (DCTELEM) wsptr[7];
shoaib_ahmed 0:791a779d6220 315 z12 = (DCTELEM) wsptr[1] - (DCTELEM) wsptr[7];
shoaib_ahmed 0:791a779d6220 316
shoaib_ahmed 0:791a779d6220 317 tmp7 = z11 + z13; /* phase 5 */
shoaib_ahmed 0:791a779d6220 318 tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */
shoaib_ahmed 0:791a779d6220 319
shoaib_ahmed 0:791a779d6220 320 z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */
shoaib_ahmed 0:791a779d6220 321 tmp10 = z5 - MULTIPLY(z12, FIX_1_082392200); /* 2*(c2-c6) */
shoaib_ahmed 0:791a779d6220 322 tmp12 = z5 - MULTIPLY(z10, FIX_2_613125930); /* 2*(c2+c6) */
shoaib_ahmed 0:791a779d6220 323
shoaib_ahmed 0:791a779d6220 324 tmp6 = tmp12 - tmp7; /* phase 2 */
shoaib_ahmed 0:791a779d6220 325 tmp5 = tmp11 - tmp6;
shoaib_ahmed 0:791a779d6220 326 tmp4 = tmp10 - tmp5;
shoaib_ahmed 0:791a779d6220 327
shoaib_ahmed 0:791a779d6220 328 /* Final output stage: scale down by a factor of 8 and range-limit */
shoaib_ahmed 0:791a779d6220 329
shoaib_ahmed 0:791a779d6220 330 outptr[0] = range_limit[(int) IRIGHT_SHIFT(tmp0 + tmp7, PASS1_BITS+3)
shoaib_ahmed 0:791a779d6220 331 & RANGE_MASK];
shoaib_ahmed 0:791a779d6220 332 outptr[7] = range_limit[(int) IRIGHT_SHIFT(tmp0 - tmp7, PASS1_BITS+3)
shoaib_ahmed 0:791a779d6220 333 & RANGE_MASK];
shoaib_ahmed 0:791a779d6220 334 outptr[1] = range_limit[(int) IRIGHT_SHIFT(tmp1 + tmp6, PASS1_BITS+3)
shoaib_ahmed 0:791a779d6220 335 & RANGE_MASK];
shoaib_ahmed 0:791a779d6220 336 outptr[6] = range_limit[(int) IRIGHT_SHIFT(tmp1 - tmp6, PASS1_BITS+3)
shoaib_ahmed 0:791a779d6220 337 & RANGE_MASK];
shoaib_ahmed 0:791a779d6220 338 outptr[2] = range_limit[(int) IRIGHT_SHIFT(tmp2 + tmp5, PASS1_BITS+3)
shoaib_ahmed 0:791a779d6220 339 & RANGE_MASK];
shoaib_ahmed 0:791a779d6220 340 outptr[5] = range_limit[(int) IRIGHT_SHIFT(tmp2 - tmp5, PASS1_BITS+3)
shoaib_ahmed 0:791a779d6220 341 & RANGE_MASK];
shoaib_ahmed 0:791a779d6220 342 outptr[3] = range_limit[(int) IRIGHT_SHIFT(tmp3 + tmp4, PASS1_BITS+3)
shoaib_ahmed 0:791a779d6220 343 & RANGE_MASK];
shoaib_ahmed 0:791a779d6220 344 outptr[4] = range_limit[(int) IRIGHT_SHIFT(tmp3 - tmp4, PASS1_BITS+3)
shoaib_ahmed 0:791a779d6220 345 & RANGE_MASK];
shoaib_ahmed 0:791a779d6220 346
shoaib_ahmed 0:791a779d6220 347 wsptr += DCTSIZE; /* advance pointer to next row */
shoaib_ahmed 0:791a779d6220 348 }
shoaib_ahmed 0:791a779d6220 349 }
shoaib_ahmed 0:791a779d6220 350
shoaib_ahmed 0:791a779d6220 351 #endif /* DCT_IFAST_SUPPORTED */